Large Eddy Simulation of Air Escape through a Hospital Isolation Room Single Hinged Doorway—Validation by Using Tracer Gases and Simulated Smoke Videos

Saarinen, Pekka E.; Kalliomäki, Petri; Tang, Julian W.; Koskela, Hannu

The two tracer gases used in the measurements were N 2 O and SF 6 , having characteristic infrared absorption bands well apart from each other and from the strongest bands of H 2 O and CO 2 . Prior to their release into the rooms, they were diluted with clean air to prevent them from stratifying near the floor. The gases were initially dosed into different rooms, but mixing was taking place during repeated door and passage cycles, whereupon calculation of the AVMs from the measured concentrations was based on Eq (1). The concentrations of both the tracers in both the rooms were monitored by one gas analyzer (BK1302) taking the sample through sampling tubes that were perforated throughout their lengths. In addition, after the door had closed, the air in the rooms was mixed by fans. These actions were necessary to ensure the sample taken by the gas analyzer is representative of the overall conditions in the room. A third measure of confirmation was use of repeated measurements, as mentioned above. The door and passage cycle was repeated and measured 6 times (7 times in the case without passage). The results were scattered without a clear increasing or decreasing trend. To ensure proper flushing of the sampling tube, the gas analyzer took the sample from the exhaust tube of a more powerful pump. The photoacoustic sample cell of the analyzer was very small, with a volume of 3 cm 3 . It was flushed with a flow rate of 5 cm 3 /s, giving a time constant less than one second. The flush time used was much longer than that, since there was no need to sample during the door cycle.